The Bristol Pegasus engine was a piston radial machine used as the powerplant of the Fairey Swordfish biplane, the Short Sunderland flying boat, and the Vickers Wellington bomber. It was reliable, easy to do maintenance on, and economic at a time when the jet engine had not yet been designed and developed.
The Bristol Pegasus engine was developed and built in different variants. The IIIM3 was a 9-cylinder, air-cooled radial engine, delivering 690 HP. This machine powered the Fairey Swordfish Mk I. The Mk II and Mk III versions of this biplane, on the other hand, were driven by the Pegasus XXX, producing 750 HP. This engine was a development of the IIIM3.
The Short Sunderland and the Vickers Wellington aircraft were powered by the Bristol Pegasus Mk XVIII, which put out 1,050-HP. This radial engine was slightly larger in diameter than the variants mentioned above, even though they all had 9 cylinders. These engines were surrounded by Townend Ring, which incorporated the exhaust collector ring at the front.
The valves of the Bristol Pegasus engine were of rocker-boxes design and they were lubricated by oil pads that were located on top of the cylinder heads. The differences among the variants lay in the propeller reduction gear ratios, static compression ratios, and accessories.
Below, the Bristol Pegasus engine IIIM3, which generated 690 horse power and turned a three-bladed propeller.
The Fairey-Reed propeller on the Bristol Pegasus IIIM3 mounted on the Swordfish biplane.
